Light-emitting element including a fusion-bonding portion on contact electrodes

ABSTRACT

A solid-state device having: a flip-chip mounted solid-state element; a power receiving/feeding portion having a mounting substrate to allow that a mounting surface of the solid-state element forms substantially the same plane as a surface of the mounting substrate; and an inorganic sealing portion made of an inorganic sealing material having a thermal expansion coefficient equal to that of the power receiving/feeding portion for sealing the solid-state element.

The present Application is a Divisional Application of U.S. patentapplication Ser. No. 11/220,405 filed on Sep. 7, 2005 now U.S. Pat. No.7,417,220.

The present application is based on Japanese patent application Nos.2004-263097 and 2004-316007, the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid state device, and particularly,to a solid state device which is sealed with a sealing material made oflow melting point glass.

The present invention also relates to a light-emitting element made of asemiconductor material and a light-emitting device using thelight-emitting element, and particularly, to a light-emitting elementand a light-emitting device which are flip-chip mounted.

Herein, a solid state device includes various optical devices orelements such as a light-emitting device or element, a light-receivingdevice or element, and a solar cell. Also, herein, a light-emittingelement includes an LED element, and a light-emitting device includes anLED.

2. Description of the Related Art

Conventionally, there are solid state devices with a solid statecomponent such as a light-emitting diode (LED), or the like, sealed witha light-transmitting resin material such as epoxy resin, or the like. Itis known that in such solid state devices, light-transmitting resin isdegraded by light. Particularly, in the case of use of group IIInitride-based compound semiconductor light-emitting elements which emitshort-wavelength light, light-transmitting resin around the elements iscaused to turn yellow by high-energy light emitted from the elements andheat produced by the elements themselves, which often unnegligiblydegrades efficiency of deriving light.

To prevent degradation of such sealing materials, there have beenproposed light-emitting devices using low melting point glass as sealingmaterial (See Japanese patent application laid-open Nos. 8-102553, and11-177129, for example).

The light-emitting device of Japanese patent application laid-open No.8-102553 is constructed by covering an LED element, wire bondingportions, and upper ends of leads, with a transparent sealing materialmade of low melting point glass. In the low melting point glass, thereis used glass whose melting point is 130-350° C. by adding theretoselenium, thallium, arsenic, sulfur, etc., for example. In this case,there is used low melting point glass whose melting point is preferably200° C. or less, more preferably 150° C. or less.

The light-emitting device of Japanese patent application laid-open No.8-102553 uses a transparent sealing material made of low melting pointglass, thereby obviating the problem with optical degradation with timeof light-transmitting resin material due to ultraviolet rays.

On the other hand, the light-emitting device of Japanese patentapplication laid-open No. 11-177129 uses, as sealing material forcovering its LED element, low melting point glass whose refractive indexis on the order of 2 close to the refractive index of GaN-based LEDelements, the order of 2.3.

The light-emitting device of Japanese patent application laid-open No.11-177129 seals its LED element with low melting point glass whoserefractive index is close to the refractive index of GaN-based LEDelements, thereby lessening light totally reflected off the interfacebetween the LED element and the low melting point glass, whileincreasing light radiated outwardly from the LED element and passed intothe low melting point glass. As a result, the outward radiationefficiency becomes higher than that of conventional light-emittingdevices with an LED element sealed with epoxy resin.

According to conventional solid state devices, however, because of highviscosity of conventional low melting point glass in a practical sealingtemperature range, it is impossible to realize a solid state devicehaving the sufficient sealing property when using a sealing materialmade of low melting point glass.

Conventionally, on the other hand, flip-chip mounting is known in whichan LED element is electrically connected to a wiring pattern of aprinted wiring board or the like through a stud bump of Au or the like.

In flip-chip mounting, a cathode and an anode on the LED element areconnected to a wiring pattern via a stud bump, thus allowing mounting ofthe LED element without using pad electrodes and wires. In addition,light is radiated from the surface opposite the mounting surface, whichthus allows excellent light-radiating performance without pad electrodesand wires blocking off light.

The above-mentioned flip-chip mounting requires arrangement of studbumps according to the number of cathodes and anodes, and stablearrangement of the LED element requires 3 or more stud bumps. Thisrequires time-consuming and costly bump formation. Particularly, inlarge-size LED elements, a plurality of stud bumps are arranged formultipoint joining, which can therefore be more significantlytime-consuming and costly.

As a means for obviating time-consuming labor in such bump formation,there is a bump formation method in which a bump for mounting componentsis formed on the surface of a printed wiring board by plating (SeeJapanese patent application laid-open No. 2002-9427).

According to a bump formation method described in Japanese patentapplication laid-open No. 2002-9427, a resist film is formed by applyingresist to the surface of a printed wiring board, using a spin coater ora printing method. The resist film formation is followed by lightexposure using a mask having a mask window matching a desired positionand shape of a bump. Next, an exposed portion is developed and dissolvedby an immersion or spray method used in typical photoresist developmentto form an opening, followed by plating the opening and subsequentlydissolving and removing the resist film, thereby forming a plurality ofbumps for mounting components on the printed wiring board.

In the above-mentioned bump formation method, however, because the bumpsfor mounting components have to be formed by photolithography, thenumber of fabrication steps increases, which results in a high cost.

Further, it is required that the bumps for mounting components have highshape accuracy matching electrode shape of the light-emitting element,and that the light-emitting element be positioned accurately relative tothe bumps for mounting components when mounting the light-emittingelement.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a solid state devicehaving the sufficient sealing property when using a sealing materialmade of low melting point glass.

It is a further object of the present invention to provide a solid statedevice which is excellent in solid state component packaging, sealing,electrical connection, and thermal dissipation.

It is a still further object of the present invention to provide an LEDelement and a light-emitting device, the packaging process of which canbe simplified.

(1) According to a first aspect of the invention, a solid-state devicecomprises:

a flip-chip mounted solid-state element;

a power receiving/feeding portion comprising a mounting substrate toallow that a mounting surface of the solid-state element formssubstantially the same plane as a surface of the mounting substrate; and

an inorganic sealing portion made of an inorganic sealing materialhaving a thermal expansion coefficient equal to that of the powerreceiving/feeding portion for sealing the solid-state element.

(2) According to a second aspect of the invention, a light-emittingelement comprises:

p and n contact electrodes formed on a flip-chip mounting surface of thelight-emitting element corresponding to one light-emitting layer of thelight-emitting element; and

a fusion-bonding portion formed on the p and n contact electrodescorresponding to the p and n contact electrodes, for being fusion-bondedto an external mounting pattern.

(3) According to a third aspect of the invention, a light-emittingdevice comprises:

a light-emitting element comprising on a flip-chip mounting surface acontact electrode which serves as a reflection mirror, and afusion-bonding portion formed on the contact electrode;

a mounting substrate comprising an external mounting patternfusion-bonded to the fusion-bonding portion; and

a light-transmitting sealing portion for sealing the light-emittingelement fusion-bonded to the mounting substrate.

(4) According to a fourth aspect of the invention, a light-emittingdevice comprises:

a light-emitting element comprising on a flip-chip mounting surface acontact electrode which serves as a reflection mirror;

a mounting substrate comprising a fusion-bonding portion fusion-bondedto the contact electrode; and

a light-transmitting sealing portion for sealing the light-emittingelement fusion-bonded to the mounting substrate.

According to the present invention, it is possible to realize a solidstate device having the sufficient sealing property when using a sealingmaterial made of low melting point glass.

According to the present invention, it is possible to provide a solidstate device which is excellent in solid state component packaging,sealing, electrical connection, and thermal dissipation.

According to the LED element and the light-emitting device of thepresent invention, since in the element fabrication process thefusion-bonded portion is electrically connected to the n-side and p-sideof the LED element so as to be formed integrally with the LED element,the mounting process can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments according to the invention will be explainedbelow referring to the drawings, wherein:

FIG. 1 is a cross-sectional view illustrating an LED as a solid statedevice according to a first embodiment of the invention;

FIG. 2 is a cross-sectional view illustrating an LED as a solid statedevice according to a second embodiment of the invention;

FIG. 3 is a cross-sectional view illustrating an LED as a solid statedevice according to a third embodiment of the invention;

FIG. 4 is a cross-sectional view illustrating an LED as a solid statedevice according to a fourth embodiment of the invention;

FIG. 5 is a cross-sectional view illustrating an LED as a solid statedevice according to a fifth embodiment of the invention;

FIG. 6 is a cross-sectional view illustrating an LED as a solid statedevice according to a sixth embodiment of the invention;

FIG. 7 is a cross-sectional view illustrating an LED according to aseventh embodiment of the invention;

FIG. 8 is a plain view where the LED element according to the seventhembodiment is viewed from electrode formation surface;

FIG. 9 is a cross-sectional view of the LED element cut along line A-Aof FIG. 8;

FIG. 10 is an enlarged cross-sectional view illustrating an LED elementaccording to an eighth embodiment of the invention;

FIG. 11A is a plain view illustrating a fusion-bonded portion of an LEDelement according to a ninth embodiment of the invention;

FIG. 11B is a cross-sectional view cut along line A-A of FIG. 11A;

FIGS. 12A and 12B are plain views illustrating a fusion-bonded portionof an LED element according to a tenth embodiment of the invention;

FIG. 13 is a plain view illustrating a fusion-bonded portion of an LEDelement according to an eleventh embodiment of the invention;

FIG. 14 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a twelfth embodiment of the invention;

FIG. 15 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a thirteenth embodiment of the invention;

FIG. 16 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a fourteenth embodiment of the invention;

FIG. 17A is a plain view illustrating a fusion-bonded portion of an LEDelement according to a fifteenth embodiment of the invention;

FIG. 17B is a cross-sectional view cut along line A-A of FIG. 17A; and

FIG. 18 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a sixteenth embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 is a cross-sectional view illustrating an LED as a solid statedevice according to a first embodiment of the invention.

This LED 1 comprises a flip-chip-type LED element 2 made of a GaN-basedsemiconductor material (thermal expansion coefficient α: 5−7 (×10 ⁻⁶/°C.)), a glass-containing Al₂O₃ substrate 3 as an inorganic materialsubstrate for mounting the LED element 2, a circuit pattern 4 consistingof tungsten (W)-nickel (Ni)-gold (Au) and formed in the glass-containingAl₂O₃ substrate 3, a conductive adhesive 5 made of Ag paste forelectrically connecting the circuit pattern 4 to a p-electrode 24 and ann-electrode 25 of the LED element 2, and a glass sealing portion 6 madeof transparent glass bonded to the glass-containing Al₂O₃ substrate 3for sealing the LED element 2. In this embodiment, the glass-containingAl₂O₃ substrate 3 and the circuit pattern 4 form a powerreceiving/feeding portion, and the joined surfaces of the p-electrode 24and the n-electrode 25 of the LED element 2 are electrically connectedto the surface of the circuit pattern 4 on substantially the same plane.

The LED element 2 is formed by sequential crystal growth of an n-GaNlayer 21, a light-emitting layer 22 and a p-GaN layer 23, via an AlNbuffer layer not shown, on the surface of a sapphire (Al₂O₃) substrate20, and has the p-electrode 24 provided on the surface of the p-GaNlayer 23, and the n-electrode 25 formed on the n-GaN layer 21 exposed byetching and removing the region extending from the p-GaN layer 23 to aportion of the n-GaN layer 21, where an insulating layer 30 is providedon the mounting surface for forming the p-electrode 24 and then-electrode 25, except for portions for electrical connection. This LEDelement 2 is epitaxially grown at 700° C. or higher, and has aheat-resistant temperature of 600° C. or higher, and is stable attemperatures at which sealing is performed using low melting pointglass, as will be described later. The p-electrode 24 is formed ofrhodium Rh for also serving as a lower reflection mirror for reflectinglight emitted from the light-emitting layer 22 in the direction of thesapphire substrate 20, and is 0.34 mm×0.34 mm×thickness 0.09 mm in size.

The glass-containing Al₂O₃ substrate 3 has a thermal expansioncoefficient of 12.3×10⁻⁶/° C., and a plurality of via holes 3A. Themetallized circuit pattern 4 on the front and back sides of thesubstrate is made electrically conductive through these via holes 3A.The circuit pattern 4 comprises a first conductive pattern formed on theLED element 2-mounting side, a second conductive pattern formed on itsback side, and a third conductive pattern made of tungsten (W) forelectrically interconnecting both the sides thereof.

The glass sealing portion 6 is formed of low melting pointP₂O₅—ZnO—Li₂O-based glass (thermal expansion coefficient: 11.4×10⁻⁶/°C.,

yield point: 415° C., refractive index n: 1.59, internal transmittance:99% (470 nm)), which is bonded to the glass-containing Al₂O₃ substrate 3by hot pressing with a mold, and thereafter is formed in a rectangularshape having a top surface 6A and side surfaces 6B formed by dicercutting.

The low melting point glass is processed with viscosity on severalorders of magnitude higher than a viscosity level which is generallysaid to be high in resin. Also, in the case of glass, its viscositycannot decrease to a general resin sealing level even if the glass is attemperatures exceeding its yield point by a few ten ° C. Also, attemptsat viscosity levels during general resin molding require temperaturesexceeding the crystal growth temperature of the LED element, or causeadhesion to a mold, which results in difficulty in sealing and molding.For this reason, the viscosity during processing is preferably 10⁴-10⁹poises.

The fabrication process for this LED 1 is explained below.

First, a glass-containing Al₂O₃ substrate 3 having via-holes 3A isprepared, and tungsten paste is screen-printed on the surface of theglass-containing Al₂O₃ substrate 3 according to a circuit pattern 4.

Next, the W-paste-printed glass-containing Al₂O₃ substrate 3 is heatedat a little more than 1000° C., thereby burning W into theglass-containing Al₂O₃ substrate 3, followed by Ni and Au plating overW, which results in the formation of a circuit pattern 4.

Next, high-viscous Ag paste is screen-printed on the surface of thecircuit pattern 4 of the glass-containing Al₂O₃ substrate 3 (on theelement-mounting side) as a conductive adhesive 5. An LED element 2 ispositioned relative to this Ag-paste-printed circuit pattern 4, andheated at 150° C., thereby hardening the Ag paste. The LED element 2 ismounted so that the mounting surfaces of its p-electrode 24 andn-electrode 25 are on substantially the same plane relative to thesurface of the circuit pattern 4.

Next, a low melting point P₂O₅—ZnO—Li₂O-based glass board is setparallel to the LED-element-mounted glass-containing Al₂O₃ substrate 3,followed by hot pressing at a temperature of 500° C. in nitrogenatmosphere. The viscosity of the low melting point glass in thiscondition is 10⁸-10⁹ poises, and the low melting point glass is bondedto the glass-containing Al₂O₃ substrate 3 via the oxides containedtherein.

Next, the glass-containing Al₂O₃ substrate 3 integral with the lowmelting point glass is set and diced in a dicer into the LED 1separately.

There may be used the LED element 2 formed by scribing. In this case,because the LED element 2 formed by scribing tends to have uneven sidesurfaces with protrusions that are cut portions, it is desired to coatthe side surfaces of the LED element 2 with an element-coating material.As this element-coating material, there may be used an SiO₂-basedcoating material having light transmittance, for example. Use of anelement-coating material allows preventing cracks and voids fromoccurring during resin overmolding, etc.

The effects of the first embodiment are as follows.

(1) Since the low melting point P₂O₅—ZnO—Li₂O-based glass is used andhot-pressed in a high viscous state, processing is possible atsufficiently low crystal growth temperatures, thus enhancing sealing.

(2) Since the glass-containing Al₂O₃ substrate 3 and the glass sealingportion 6 are chemically bonded to each other via the oxide, firmsealing bonding strength can be obtained. For that reason, glass sealingis materialized even in the case of small-size packages with smalljoining area.(3) Since the sealing glass and the glass-containing Al₂O₃ substrate 3have the same thermal expansion coefficient, after high temperaturebonding, internal stress is small even at normal or low temperature,there is a less incidence of bonding failures of peeling, cracking, etc.In addition, glass tends to be caused to crack due to tensile stress,but has a less incidence of cracking due to compressive stress, so thethermal expansion coefficient of the sealing glass is made slightlysmall compared to the glass-containing Al₂O₃ substrate 3. The inventorhas confirmed that no peeling and cracking occur even at 1000 cycles of−40° C.<→100° C. liquid phase cold thermal shock tests. Also, as basicconfirmation of bonding of a 5 mm square size glass piece to a ceramicsubstrate, experiments of combinations of various thermal expansivitiesof glass and ceramic substrate have verified that bonding is possiblewithout cracking when the ratio of the low to high thermal expansioncoefficient member is 0.85 or more. Although depending on the stiffnessand size of the members, the same thermal expansion coefficientindicates this extent of range.(4) Since no wire is required by flip-chip mounting, no malfunction ofelectrodes occurs in high viscous processing. Since the viscosity of thelow melting point glass during sealing is as hard as 10⁸-10⁹ poiseswhich is significantly different in material properties compared to theorder of 5 poises of liquid epoxy resin prior to thermal curing, noproblems such as wire crushing and deformation occur when a face-up LEDelement is sealed in which electrodes on element surface andpower-feeding members such as leads are electrically connected to eachother by wires. Also, when a flip-chip LED element is sealed in whichelectrodes on element surface are flip-chip-joined to power-feedingmembers such as leads through a bump such as gold (Au), etc., it ispossible to prevent bump crushing and a short-circuit between bumps dueto pressure acting on the LED element in the direction of thepower-feeding members according to the viscosity of glass.(5) Since the low melting point glass and the glass-containing Al₂O₃substrate 3 are set parallel to each other and hot-pressed in a highviscous state, so as to move the low melting point glass parallel to thesurface of the glass-containing Al₂O₃ substrate 3 and bring it intoclose contact therewith, no void occurs in sealing the GaN-based LEDelement 2.(6) Since the circuit pattern 4 of the glass-containing Al₂O₃ substrate3 is drawn out to the backside at the via-holes 3A, there is no need oftaking a particular action for preventing glass from penetrating intounwanted portions, from covering electrical terminals, and so on,thereby allowing the simplifying of the fabrication process. Also, sincea plurality of devices are collectively sealed with the low meltingpoint glass board, a plurality of LEDs 1 can easily be mass-produced bydicer cutting. Since the low melting point glass is processed in a highviscous state, without any need of taking a sufficient action as inresin, it is sufficiently possible to treat mass-production even withoutvia-holes, provided that external terminals are drawn out to thebackside(7) Since the GaN-based LED element 2 is flip-chip mounted, there arealso the effects of being capable of overcoming the problems inmaterializing glass sealing, and of materializing 0.5 mm-squareultra-small-size LED 1. This is because no wire boding space isrequired, and no interface peeling occurs even in bonding in a smallspace by selecting the glass sealing portion 6 and the glass-containingAl₂O₃ substrate 3 with the same thermal expansion coefficient and byfirm chemical bonding.(8) Since the LED element 2 is mounted so that the mounting surfaces ofits p-electrode 24 and n-electrode 25 are on substantially the sameplane relative to the surface of the circuit pattern 4, high-viscousglass cannot penetrate between the LED element 2 and the circuit pattern4, thus allowing the prevention of a decrease in electrical connectioncharacteristics and of cracking due to glass penetration, and therebyenhancing the mounting property.(9) Since the ratio of the mounting area to the element area of the LEDelement 2 is large, thermal dissipation can be enhanced and temperatureirregularity can be prevented in the LED element 2. Also, sinceelectrical connection characteristics are enhanced by enlargedconductive area, it is possible to sufficiently treat large light amountand high power of the LED 1.(10) Since portions other than the mounting surfaces of the LED element2 are covered with the insulating layer 30, it is possible to preventleak current from flowing through the portions other than the mountingsurfaces of the LED element 2 even in the event of Ag paste adhesionthereto.

In the first embodiment, although Ag paste is used as the conductiveadhesive 5, there may be used any conductive adhesive 5 other than Agpaste, which has material properties that do not lose the mountingproperty of the LED element 2 due to pressure exertion during glasssealing.

Also, if applicable to flip-chip mounting, any type of LED element maybe used other than the GaN-based LED element 2. Also, as an opticalelement other than the LED element, there may be used a light-receivingelement.

Embodiment 2

FIG. 2 is a cross-sectional view illustrating an LED as a solid statedevice according to a second embodiment of the invention. In thefollowing embodiments, the same reference numbers as those of the firstembodiment respectively denote the portions having the same structureand function as those in the first embodiment.

This LED 1 is different from that of the first embodiment inscreen-printing high viscous Ag paste as the conductive adhesive 5 on aportion positioned on the n-electrode 25 of the LED element 2 explainedin the first embodiment, and bringing the p-electrode 24 into closecontact with the circuit pattern 4 directly without Ag pastetherebetween.

The effects of the second embodiment are as follows.

(1) Since no internal stress occurs in glass at high temperatures duringglass processing, but glass contracts as cooled, which causescompression stress from the glass sealing portion 6 and the sapphiresubstrate 20 to the LED element 2, the element-mounting surface of thep-electrode 24 comes into close contact with the mounting surface of thecircuit pattern 4 on substantially the same plane. This allowsexcellent-reliability electrical connection to be obtained without usingAg paste.

In flip-chip mounting using an Au-stud bump with epoxy resin and siliconresin, breaking can often be caused by tensile stress of the resin insolder reflow furnace treatment. This is because the resin with largerthermal expansion coefficient than that of the LED element 2 expandsrelatively more in higher-temperature atmosphere than resin-curingtemperature. In contrast, in the solid state device of the invention,even in lead-free solder reflow furnace atmosphere on the order of 300°C., which is lower than glass sealing temperature, compression stresstherefore continues to act on the LED element 2, which results in nobreaking.

Here, if no position shift of the LED element 2 occurs relative to thecircuit pattern 4, glass sealing may be performed with low melting pointglass by arranging the n-electrode 25 at a specified position on thecircuit pattern 4 without fixing the n-electrode 25 with Ag paste. Also,even in the case of positioning by bonding, portions other than themounting surfaces may be temporarily bonded with not conductive butthermal resistive adhesive

Embodiment 3

FIG. 3 is a cross-sectional view illustrating an LED as a solid statedevice according to a third embodiment of the invention.

This LED 1 is different from that of the first embodiment in that, tomake possible electrical connection on the element side surfaces andsurface mounting on the semiconductor layer side, an LED element 2 witha p-electrode 24 and an n-electrode 25 formed so as to be exposed toelement edges from the element side surfaces to p-contact layer 240surface are mounted on a circuit pattern 4 provided on an Al₂O₃substrate 300 (thermal expansion coefficient: 7×10⁻⁶/° C.), and sealedwith a glass sealing portion 6 made of SiO₂—Nb₂O₅-based low meltingpoint glass. Here, the term “element edges” refers to edges of sidesurfaces of the LED element 2, and GaN-based semiconductor layermounting surface formed in an insulating layer 31, as shown in FIG. 3.

The LED element 2 comprises an AlN buffer layer 200, an n-GaN layer 21,a light-emitting layer 22, a p-GaN layer 23, and a p-contact layer 240for diffusing current into the p-GaN layer 23, which are sequentiallystacked on a sapphire substrate 20, a light-transmitting insulatinglayer 30 on the side surfaces of the GaN-based semiconductor layer, ann-electrode 25 formed on the n-GaN layer 21 exposed by etching andremoving the region extending from the p-GaN layer 23 to a portion ofthe n-GaN layer 21, a p-electrode 24 provided on the side surfaces ofthe GaN-based semiconductor layer extending from the AlN buffer layer200 on the sapphire substrate 20 to the p-contact layer 240, and alight-transmitting insulating layer 31 for covering the element surfaceextending from the n-electrode 25 to the p-electrode 24.

The Al₂O₃ substrate 300 has a thin-film conductive plating layer 40 madeof solder formed by electroplating the surface of the circuit pattern 4.

The fabrication process for this LED 1 is explained below.

First, the conductive plating layer 40 is formed by solderelectroplating on the surface of the circuit pattern 4 that is providedon the Al₂O₃ substrate 300 for serving as an element mounting surface.

Next, the LED element 2 is positioned so that the formation surface ofthe insulating layer 31 comes into close contact with a specifiedposition on the circuit pattern 4. Next, the Al₂O₃ substrate 300 withthe LED element 2 positioned thereon is put and heated in a reflowfurnace. This heating allows the conductive plating layer 40 to fuse sothat the mounting surfaces of the p-electrode 24 and n-electrode 25 aresoldered to the element-mounting surface of the circuit pattern 4 onsubstantially the same plane.

Next, an SiO₂—Nb₂O₅-based low melting point glass board is set parallelto the LED-element 2-mounted Al₂O₃ substrate 300, followed by hotpressing at a temperature of 500° C. in nitrogen atmosphere. Theviscosity of the low melting point glass in this condition is 10⁸-10⁹poises, and the low melting point glass is bonded to the Al₂O₃ substrate300 via the oxides contained therein.

Next, the Al₂O₃ substrate 300 integral with the low melting point glassis set and diced in a dicer into the LED 1 separately.

The effects of the third embodiment are as follows.

(1) Since the LED element 2 with the p-electrode 24 and n-electrode 25exposed from the mounting surface to the side surfaces is mounted so asto come into contact with the circuit pattern 4, glass penetration tothe mounting surface is blocked during glass sealing, thereby allowingobtaining effective joining area. This allows heat caused by lightemission of the light emitting layer 22 to be promptly thermallyconducted to the Al₂O₃ substrate 300, thus allowing enhancement inthermal dissipation.(2) Since the p-electrode 24 and n-electrode 25 are joined to thecircuit pattern 4 via the conductive plating layer 40 made of solder, nosolder adheres to portions other than the electrodes, thus allowingprevention of a decrease in electrical connection characteristics due toleak current.(3) Because of the surface mounting of the LED element 2 with theelectrodes formed so as to be exposed to element edges, the occupationratio of light emitting area to the entire element can be large, thusallowing ensuring high brightness.(4) Since the solder is made in a thin film shape by plating, thespacing between the p-electrode 24 and n-electrode 25 can be narrow, andthere can be a less incidence of short-circuiting.

In the third embodiment, although the LED 1 has the LED element 2 withthe electrodes exposed to element edges, the LED element 2 explained inthe first embodiment may be joined to the circuit pattern 4 via theconductive plating layer 40. In this case, because of no solderpenetration into portions other than mounting surface, no decrease iscaused in electrical characteristics due to leak current.

Also, in the case of use of the LED element 2 explained in the firstembodiment, the insulating layer 30 for preventing a short-circuit ofthe p-electrode 24 and n-electrode 25 may be omitted

Embodiment 4

FIG. 4 is a cross-sectional view illustrating an LED as a solid statedevice according to a fourth embodiment of the invention;

This LED 1 is different from that of the third embodiment in structurehaving an LED-element 2 on the order of light emission peak wavelength380 nm, and a conductive plating layer 40 made of an Ni layer 41 and anAu layer 42 formed on a p-electrode 24 and n-electrode 25 of theLED-element 2.

The conductive plating layer 40 is constructed by forming a 20 μm thickNi-layer 41 on the surfaces of the p-electrode 24 and n-electrode 25,and forming thereon an Au layer 42 by flash plating. This conductiveplating layer 40 allows the Au layer 42 to be fused by thermocompressionbonding combined with ultrasound so that the mounting surfaces of thep-electrode 24 and n-electrode 25 are joined to the element-mountingsurface of the circuit pattern 4 on substantially the same plane.

The effects of the fourth embodiment are as follows.

(1) Since the conductive plating layer 40 consists of Ni and Au, theconductive plating layer 40 fused during mounting the LED-element 2cannot again be fused by heat during glass sealing, and the LED-element2 once fixed is thereby not shifted in position during glass sealing sothat the fixed state is stable, thus allowing ensuring enhancement insealing and reliability.(2) Since light of the order of 380 nm emitted from the LED element 2 issealed by the glass sealing portion 6 with durability, there can easilybe materialized a near-ultraviolet light LED 1 with light-emissioncharacteristics which is stable over a long period of time.(3) If the temporal bonding is possible during mounting the LED-element2, the subsequent glass sealing allows the joining of the LED-element 2and the Al₂O₃ substrate 300 to be ensured by compressive stress. This isbecause of the shape effect of positioning the LED-element 2 in themiddle of a solid-state device, in the case of the thermal expansioncoefficient of the glass sealing portion 6 being equal to as well aslarger than that of the LED-element 2. It should be noted that, in caseof the thermal expansion coefficient of the glass sealing portion 6being 4 times or more that of the LED-element 2, cracking is caused inthe glass, depending on the size of the LED-element 2 and the materialproperties of the glass.

Embodiment 5

FIG. 5 is a cross-sectional view illustrating an LED as a solid statedevice according to a fifth embodiment of the invention.

This LED 1 is different from that of the fifth embodiment in structurehaving on the element-mounting surface of the circuit pattern 4 theconductive plating layer 40 explained in the fourth embodiment.

The effects of the fifth embodiment are as follows.

Since the mounting surfaces of the p-electrode 24 and n-electrode 25 arejoined to the element-mounting surface of the circuit pattern 4 onsubstantially the same plane by thermocompression bonding combined withultrasound without forming the conductive plating layer 40 on theLED-element 2, stable element fixation can be realized without platingthe existing LED-element 2, allowing ensuring enhancement in sealing andreliability, in addition to the favorable effects of the fourthembodiment.

Embodiment 6

FIG. 6 is a cross-sectional view illustrating an LED as a solid statedevice according to a sixth embodiment of the invention.

This LED 1 is different from that of the fourth embodiment in structurehaving a coating layer 10 made of TiO₂ having anatase structure on thesurface of the glass sealing portion 6 of the LED 1 explained in thefourth embodiment, where organics in air are captured and decomposed byoptical catalytic action of TiO₂ excited by light of the order of 380 nmpeak wavelength radiated from the LED element 2.

The effects of the sixth embodiment are as follows.

Since the coating layer 10 is formed over the glass sealing portion 6,and TiO₂ constituting the coating layer 10 is therefore uniformlyirradiated with light radiated from the LED element 2, thereby allowingenhancement in optical catalytic action. Also, in resin sealing, thesealing resin itself of the LED element 2 deteriorates due to opticalcatalytic action, but since the glass sealing portion 6 is formed ofstable inorganic material, the function as an optical catalytic devicecan be performed without optical deterioration over a long period oftime.

The glass sealing portion 6 is stable to light, but there is alsomaterial which is made turbid white by moisture caused by organicdecomposition adhering to its surface for a long period of time. In thiscase, in order to prevent this, a light-transmitting MgF coating, forexample, may be applied to the surface of the glass sealing portion 6,followed by forming thereover a further coating layer 10.

In the sixth embodiment, although the coating layer 10 is formed as anoptical catalytic portion over the surface of the LED 1, an opticalcatalytic portion made of beads of TiO₂ particles and having airpermeability between beads may be disposed around the LED 1.

In the above embodiments, although the sealing material of the LEDelement 2 is glass, a portion of glass may be crystallized and turbidwhite according to uses, and material is not limited to a glass state,provided that good joining to a power receiving/feeding portion withchemically stable inorganic material is possible.

Also, although the LED using the LED element as the solid state devicehas been explained, the solid state device is not limited to the LEDelement, but may be another optical element such as a light-receivingelement, solar cell, or the like.

Embodiment 7

FIG. 7 is a cross-sectional view illustrating an LED according to aseventh embodiment of the invention.

This LED 101 is formed by mounting a plurality of LED elements on awafer substrate, sealing them from above, thereby forming a plurality ofLEDs and cutting them with a dicer.

The LED 101 comprises a flip-chip-type LED element 102 made of anitride-based compound semiconductor material (thermal expansioncoefficient α: 7×10⁻⁶/° C.), an Al₂O₃ substrate 103 as an inorganicmaterial substrate for mounting the LED element 102, circuit patterns104A and 104B and a via pattern 104C consisting of tungsten (W)-nickel(Ni)-gold (Au) and formed in the Al₂O₃ substrate 103 a fusion bondingportion 105 consisting of Ni thick film and Au on the surface of ap-electrode and an n-electrode of the LED element 102, and a glasssealing portion 106 as inorganic sealing material made of transparentglass thermocompression-bonded to the Al₂O₃ substrate 103 for sealingthe LED element 102.

FIGS. 8 and 9 show the LED element used in the seventh embodiment. FIG.8 is a plain view where the LED element is viewed from electrodeformation surface, and FIG. 9 is a cross-sectional view of the LEDelement cut along line A-A of FIG. 8.

This LED element 102 has the fusion bonding portion 105 formed accordingto the shape of the p-electrode and n-electrode as shown in FIG. 8, and,as shown in FIG. 9, has a GaN-based semiconductor layer formed bysequential crystal growth of an n-GaN layer 121, a light-emitting layer122, and a p-GaN layer 123, via an AlN buffer layer not shown, on asapphire (Al₂O₃) substrate 120

The GaN-based semiconductor layer further has a p-contact electrode 124formed of rhodium Rh and on the surface of the p-GaN layer 123, and ann-contact electrode 125 formed of V/Al and on the n-GaN layer 121exposed by dry-etching and removing the region extending from the p-GaNlayer 123 to a portion of the n-GaN layer 121, where the fusion bondingportion 105 is integrally formed on the surface of the p-contactelectrode 124 and the n-contact electrode 125 by electroless plating.

Here, the n-contact electrode 125 has a necessary and sufficient sizecapable of low contact voltage to conducting current, and most of theremaining space is the p-contact electrode 124. In other words, portionother than space around the element and spacing in which the p-contactelectrode 124 and the n-contact electrode 125 do not short-circuit isoccupied by the p-contact electrode 124.

The LED element 102 is 0.34 mm×0.34 mm×thickness 0.09 mm in size, and isepitaxially grown at 700° C. or higher, and has a heat-resistanttemperature of 600° C. or higher, and is stable at temperatures at whichsealing is performed using low melting point glass, as will be describedlater. The p-contact electrode 124 is formed of rhodium Rh havingcurrent diffusivity and light reflectivity for also serving as a lowerreflection mirror for reflecting light emitted from the light-emittinglayer 122 in the direction of the sapphire substrate 120.

The Al₂O₃ substrate 103 has a thermal expansion coefficient of 7×10⁻⁶/°C., and has a plurality of via-holes 103A passing through from its frontto back side. These via-holes 103A have the via pattern 104C for makingthe metalized circuit patterns 104A and 104B conductive on the front andback side of the Al₂O₃ substrate 103.

The fusion bonding portion 105 comprises an Ni layer 150 formed in athick film shape by electroless plating on the surface of the p-contactelectrode 124 and the n-contact electrode 125, and an Au layer 151formed by flash plating on the surface of the Ni layer 150 in thefabrication process of the LED element 102, where during joining, theupper surface of the LED element 102 is formed so as to have the heightparallel to the surface of the Al₂O₃ substrate 103. Also, the Au layer151 is fused by thermocompression-bonding combined with ultrasound, andthereby joined to the circuit pattern 104B in area according to theshape of the p-contact electrode 124 and the n-contact electrode 125.The Ni layer 150 may have appropriate stiffness as the Au support layeragainst thermocompression-bonding combined with ultrasound, and may beformed of metal material such as Ag, Cu or the like.

The glass sealing portion 106 is formed of SiO₂—NbO₂-based low meltingpoint glass (thermal expansion coefficient: 7.0×10⁻⁶/° C.), andthermocompression-bonded to the Al₂O₃ substrate 103 by hot-pressing witha mold. A semi-spherical optically shaped surface 106A is formed on thelight derivation side of the glass sealing portion 106 for radiatinglight radiated from the LED element 102 in a direction based on theoptical shape. As the sealing material, it is possible to use resinsealing material such as epoxy resin, silicon resin, etc., in place ofinorganic sealing glass.

The low melting point glass is processed with viscosity on severalorders of magnitude higher than a viscosity level which is generallysaid to be high in resin. Also, in the case of glass, its viscositycannot decrease to a general resin sealing level even if the glass is attemperatures exceeding its yield point by a few ten ° C. For thisreason, in glass sealing by hot-pressing of the flip-chip mounted LEDelement 102, if there is a gap between the LED element 102 and the Al₂O₃substrate 103, there is the possibility of pressurized glass penetratingthere halfway, and causing partial peeling of electrodes, which resultsin an abnormal light-emitting pattern. The electrodes also serve as areflection film, which radiates light arriving at electrode peelingportion and radiated outwardly from GaN into the air, in a directiondifferent from its original direction.

The fabrication process for this LED 101 is explained below.

First, a glass-containing Al₂O₃ substrate 103 having via-holes 103A isprepared, and tungsten (W) paste is screen-printed on the frontside,backside and via-holes 103A of the glass-containing Al₂O₃ substrate 103according to circuit patterns 104A and 104B and a via pattern 104C.

Next, the W-paste-printed Al₂O₃ substrate 103 is heated at a little morethan 1000° C., thereby burning W into the Al₂O₃ substrate 103, followedby Ni and Au plating over W, which results in the formation of circuitpatterns 104A and 104B and a via pattern 104C.

Next, an LED element 102 is positioned relative to the circuit pattern104B. The Au layer 151 of the fusion bonding portion 105 is fused bythermocompression-bonding combined with ultrasound, and thereby joinedto the circuit pattern 104B. The LED element 102 is mounted by thefusion bonding portion 105 so that the mounting surface is onsubstantially the same plane relative to the surface of the circuitpattern 104B.

Next, a low melting point SiO₂—NbO₂-based glass board is set parallel tothe LED-element 102-mounted Al₂O₃ substrate 103, followed by hotpressing at a temperature of 500° C. in nitrogen atmosphere. Theviscosity of the low melting point glass in this condition is 10⁸-10⁹poises, and the low melting point glass is bonded to the Al₂O₃ substrate103 via the oxides contained therein.

Next, the Al₂O₃ substrate 103 integral with the low melting point glassis set and diced in a dicer into the LED 101 separately.

There may be used the LED element 102 formed by scribing. In this case,it is preferred to form a V-groove for scribing in the Al₂O₃ substrate103 beforehand, or a mark-off line.

In this LED 101, when connecting the circuit pattern 104A to a powersupply not shown to apply voltage, current is caused to flow through thevia pattern 104C, the circuit pattern 104B and the fusion bondingportion 105, to the p-contact electrode 124 and the n-contact electrode125 of the LED element 102, followed by blue light emission of the lightemission portion 122, whose light emission wavelength is 450 nm-480 nm.Of blue light emission, light radiated to the sapphire substrate 120side is passed through the sapphire substrate 120 into the glass sealingportion 106, and radiated in a direction according to optical shape inthe interface without side of the optically shaped surface 106A. Also,of blue light emission, light radiated to the p-contact electrode 124side is reflected in the direction of the sapphire substrate 120 by thep-contact electrode 124, and passed through the sapphire substrate 120into the glass sealing portion 106, and radiated outwardly via theoptically shaped surface 106A.

The effects of the seventh embodiment are as follows.

(1) Since the fusion bonding portion 105 consisting of the thick film Nilayer 150 and Au layer 151 formed on its film in thin film shape isintegrally formed in the fabrication process of the LED element 102, theconventional bump forming step can be omitted, thereby allowingenhancement in mass production and realizing low cost. Also, since aninclination of the LED element 102 that is a problem in flip-chipmounting with a stud bump is not caused even without forming 3-pointbumps, the mass productivity is excellent.(2) Since most of space other than the n-contact electrode 125 havingnecessary and sufficient size is the p contact electrode 124 matchingthe light emission layer, the occupation ratio of light emission surfaceto size of the LED element 102 can be large. The GaN-based semiconductorlayer (light emission layer) with large heat dissipation is positionedon the mounting side to the sapphire substrate 120. This allows makingcurrent density and temperature rise of the light emission layer low,and enhancing light emission efficiency and reliability.(3) Since the Ni layer 150 and Au layer 151 are formed in substantiallythe same shape of the p-contact electrode 124 and the n-contactelectrode 125 and covering its surface, joining area relative to thecircuit pattern 104B can be large, and bonding strength of the LEDelement 102 can be large, preventing peeling. Also, because of largejoining area, heat dissipation from the LED element 102 can be enhanced,handling high power.(4) Since the LED element 102 is mounted so that mounting surface andthe circuit pattern 104B are on substantially the same plane, hotpressing of low melting point glass allows preventing glass frompenetrating between the mounting surface and the circuit pattern 4, thusallowing the prevention of a decrease in electrical connectioncharacteristics and of peeling due to glass penetration to the mountingsurface, which results in a high-reliability LED 101. Also, an abnormallight emission pattern due to partial electrode peeling can beprevented.(5) Because of chemical bonding of the Al₂O₃ substrate 103 and glasssealing portion 106 via an oxide, firm bonding strength can be obtained.This can materialize glass sealing even in the case of a small packagewith joining area.(6) Since the LED element 102, the Al₂O₃ substrate 103 and glass sealingportion 106 have the same thermal expansion coefficient, thermal stressdue to a thermal expansion coefficient difference can be small duringglass sealing, and there is a less incidence of package cracking, andproductivity is excellent.

In the seventh embodiment, although the LED 101 uses the LED element 102made of GaN-based semiconductor material, the LED element 102 is notlimited thereto, but may be another LED element such as flip-chipmountable GaAs, GaP-based LED element 102. In particular, in materialwith high temperature dependency of optical power of an LED element suchas AlInGaP, AlGaAs LED element 102, the effect of enhancing thermaldissipation is large.

Also, using a fluorescent material excited by blue light radiated fromthe LED element 102, there may be used an LED 101 radiating wavelengthconversion light such as white light. As such a fluorescent material,there may be used a cerium-activated YAG (Yttrium Aluminum Garnet). TheYAG is excited by blue light to produce yellow light, thereby allowingwhite light to be obtained by complementary color of blue and yellowlight. The fluorescent material can uniformly provided by coating thesurface of the LED element 102.

Also, a plurality of LED elements 102 having the seventh embodimentstructure may be mounted on the substrate for glass sealing.

Also, the light emitting layer may be divided into two, to form LEDelements 102 having one n-contact electrode and two p-contact electrode.In this case, for one light emitting layer, there are respectivelyprovided one n-contact electrode and one p-contact electrode, but then-contact electrode is the common electrode of two light emittinglayers. Even if the light emitting layer is not divided, if thep-contact electrode is divided, because the light emitting portion isdivided virtually, which is similar to division of the light emittinglayer.

Also, in the seventh embodiment, although the fusion bonding portion 105is formed on the LED element 102, the fusion bonding portion105-applying target is not limited thereto, but may be a light receivingelement, for example.

Embodiment 8

FIG. 10 is an enlarged cross-sectional view illustrating an LED elementaccording to an eighth embodiment of the invention. In the followingembodiments, the same reference numbers as those of the seventhembodiment respectively denote the portions having the same structureand function as those in the seventh embodiment.

This LED 101 is different from that of the first embodiment in structurehaving a fusion bonding portion 130 consisting of an Ni layer 131 and anAu layer 132 formed on the Al₂O₃ substrate 103 side according to acircuit pattern, and no Ni layer on the p-contact electrode 124 and then-contact electrode 125 of the LED-element 2.

The effects of the eighth embodiment are as follows.

(1) Even by forming on the Al₂O₃ substrate 103 side the fusion bondingportion explained in the seventh embodiment, and thermocompressionbonding combined with ultrasound of the Au layer 151 formed on thep-contact electrode 124 and the n-contact electrode 125, and the Aulayer 132 of the fusion bonding portion 130, the bump forming step canbe omitted as in the seventh embodiment. Also, joining area relative tothe circuit pattern can be large, and bonding strength of the LEDelement 102 can be large, preventing peeling. Also, because of largejoining area, heat dissipation from the LED element 102 can be enhanced,handling high power.(2) Since the fusion bonding portion 130 can be formed without dependingon the size of the LED element 102, the fusion bonding portion 130 caneasily be formed, and mounting is easily possible on substantially thesame plane without requiring high positioning accuracy even in the caseof a small LED element 102.(3) Since the LED element 102 is mounted so that mounting surface andthe circuit pattern 104B are on substantially the same plane, hotpressing of low melting point glass allows preventing glass frompenetrating between the mounting surface and the circuit pattern 4, thusallowing the prevention of a decrease in electrical connectioncharacteristics and of peeling due to glass penetration to the mountingsurface, which results in a high-reliability LED 101. Also, an abnormallight emission pattern due to partial electrode peeling can beprevented.

Embodiment 9

FIG. 11A is a plain view illustrating a fusion-bonded portion of an LEDelement according to a ninth embodiment of the invention, and FIG. 11Bis across-sectional view cut along line A-A of FIG. 11A.

This LED element 102 is different from that of the seventh embodiment instructure having a circular fusion bonding portion 105 analogous to aconventional stud bump on the p-contact electrode 124 and the n-contactelectrode 125 as shown in FIG. 11A, and having an Au layer on contactelectrode surface other than the fusion bonding portion 105 as shown inFIG. 11B. In the same figure, to obtain stability during LED element 102mounting, two fusion bonding portions 105 are formed on the p-contactelectrode 124 and one fusion bonding portion 105 is formed on then-contact electrode 125, but the fusion bonding portion 105 is possibleto be formed without being limited to the number, shape, and arrangementshown.

The effects of the ninth embodiment are as follows.

In element mounting analogous to a conventional stud bump, theconventional bump forming step can be omitted, thereby allowingenhancement in mass production and realizing low cost.

The thermal dissipation and bonding strength are slightly inferior tothe seventh embodiment, but quality stability is excellent. That is,because of narrow joining area, ultrasonic power and compression bondingduring joining can be the same as conventional.

Also, joining area including the Ni layer 150 is narrow, and peripheralcrushed portion can be escaped. Because of 3 point supports, sufficientjoining of the 3 point supports can be obtained. Also, the electrode has2 terminals, but the 3 point supports allow the LED element 102 to bestably arranged.

Embodiment 10

FIGS. 12A and 12B are plain views illustrating a fusion-bonded portionof an LED element according to a tenth embodiment of the invention;

This LED 101 has a plurality of fusion bonding portions 105 in an islandform on the p-contact electrode 124 as shown in FIG. 12A.

In the fusion bonding portions 105, when the Au layer 151 is formed onthe surface of the Ni-layer 150, thick Au adheres to the peripheralportion of the Ni-layer 150, so that in the case of the large Ni-layer150, there is concern that the joining state of the Au joining surfacecan be uneven.

The effects of the tenth embodiment are as follows.

(1) Since the fusion bonding portion 105 with the same electrode isdivided into islands in the fabrication process, the Au layer 151 cancrush uniformly during thermocompression bonding combined withultrasound, which results in a uniform joining state. This allows largejoining area to be stably ensured, and thermal dissipation can beenhanced as in the seventh embodiment. Also, since the Au layer 151 cancrush uniformly, the LED element 102 can be thermocompression bondedstably without being inclined. Also, there is the effect of a lessincident of glass penetrating between the mounting surface and the LEDelement 102. Even if pressurized, because of high glass viscosity, evenin the case of no gap at all, there is the effect.

Also, except that the fusion bonding portion 105 is divided intoislands, the islands may be connected by cutting a pattern as shown inFIG. 12B. This case can yield similar effects, thereby enhancing thermaldissipation. The cut is not limited to cutting from an end portion, butmay be formed inside.

Embodiment 11

FIG. 13 is a plain view illustrating a fusion-bonded portion of an LEDelement according to an eleventh embodiment of the invention

This LED element 102 is different from that of the seventh embodiment instructure having the fusion bonding portion 105 explained in the seventhembodiment, formed on the n-contact electrode 125 provided at the centerof the LED-element 2, and annularly along the peripheral portion of thep-contact electrode 124.

The n-side fusion bonding portion 105 has the n-GaN layer 121 exposed bydry-etching the GaN-based semiconductor layer at the center of theLED-element 2, an n-contact electrode formed on the exposed portion ofthe n-GaN layer 121, an Ni-layer 150 thereon formed in a thick filmshape, and an Au layer 151 subsequently formed, which is thereby formedsmaller than the n-side fusion bonding portion 105 explained in theseventh embodiment

The effects of the eleventh embodiment are as follows.

(1) Since the n-side fusion bonding portion 105 is made small at thecenter of a light emission region, and p-side fusion bonding portion 105is formed annularly in the peripheral portion, the area of the p-contactelectrode 124 relative to the light emitting layer 122 of theLED-element 2 can be enlarged, enhancing current diffusivity to thep-GaN layer 123. Namely, the occupation ratio of the light emissionregion of the LED-element 2 is made large, thereby realizing highbrightness.(2) The p-side fusion bonding portion 105 is formed annularly around thep-contact electrode 124, the sealing material can be prevented frompenetrating into the inner side than p-side fusion bonding portion 105,thus allowing the prevention of electrode damage and a decrease inelectrical connection characteristics and of peeling due to glasspenetration between the LED element 102 and the circuit pattern. Sincethe bonding strength of the LED element 102 can be large, there is aless incidence of peeling and high-reliability flip-chip mounting ispossible. There is a less incidence of abnormal light emission pattern.

AS explained in the seventh embodiment, in the case of use of sealingglass, at high temperatures, no stress is caused in the peelingdirection of the sealing portion, no high bonding strength is requiredfor sealing with sealing resin. For that, the p-side fusion bondingportion 105 is not entirely but partially annular, thereby obtainingpractical bonding strength.

Embodiment 12

FIG. 14 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a twelfth embodiment of the invention.

This LED element 102 is different from that of the eleventh embodimentin structure having the n-side fusion bonding portion 105 provided atthe center of the LED-element 102, the 10 μm wide n-contact electrode125 radially formed for being electrically connected to the n-sidefusion bonding portion 105, 4-point p-side fusion bonding portion 105formed on the p-contact electrode 124.

The effects of the twelfth embodiment are as follows.

In addition to the favorable effects of the seventh and eleventhembodiments, the n-contact electrode 125 radially formed from the centerof the LED-element 102 allows enhancement in current diffusivity.Further, the n-contact electrode 125 can be as thin as 20 μm or less inwidth because of no thick film Ni layer 150. The current diffusivity canbe enhanced without significantly decreasing the area of the p-contactelectrode 124 which serves as light emission area.

As explained in the eleventh embodiment, the p-side fusion bondingportion 105 may be formed annularly around the p-contact electrode 124,thus allowing the prevention of electrode damage and a decrease inelectrical connection characteristics.

Embodiment 13

FIG. 15 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a thirteenth embodiment of the invention.

This LED element 102 is different from that of the eleventh in structureusing a smaller-size LED element 102 (0.2 mm×0.2 mm) compared to the LEDelement 102 explained in the seventh to twelfth embodiment, and havingan n-side fusion bonding portion 105 provided at the center of theLED-element 102, as in the eleventh embodiment, and a p-side fusionbonding portion 105 provided at 4 corners of the p-contact electrode124. The n-side fusion bonding portion 105 is formed at a size ratio tothe entire area of the LED element 102 which does not degrade lightemission efficiency.

The effects of the thirteenth embodiment are as follows.

Since the n-side fusion bonding portion 105 matching the size of theLED-element 102 is formed at the center of the LED-element 102, inaddition to the favorable effects of the twelfth embodiment, asmall-size but high-brightness LED-element 102 can be obtained withoutsignificantly decreasing the occupation ratio of the light emission areato the LED-element 102. 70% of blue light produced by the light emissionlayer 122 of the GaN-based LED-element 102 is lateral propagation lightwithin the GaN-based semiconductor layer, so light cannot be radiatedoutwardly. Also, light derivation efficiency is degraded due to anincrease in lateral propagation distance, and absorption by repeatedreflection at the reflection surface.

Namely, by making the LED-element 102 small, the lateral propagationdistance shortening and the number of reflection can be reduced. Asexplained in this embodiment, when the GaN-based LED-element 102 isformed with 0.2 mm×0.2 mm, light derivation efficiency is enhanced by20%, compared to the LED-element 102 formed with 0.34 mm×0.34 mmexplained in the seventh embodiment. Also, when the GaN-basedLED-element 102 is formed with 0.1 mm×0.1 mm, light derivationefficiency is enhanced by 40%.

Also, in the thirteenth embodiment, as explained in the eleventhembodiment, the p-side fusion bonding portion 105 may be formedannularly around the p-contact electrode 124.

Embodiment 14

FIG. 16 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a fourteenth embodiment of the invention.

This LED element 102 is different from that of the twelfth in structureforming a rectangular LED element 102 (0.1 mm×0.34 mm) and having ann-side fusion bonding portion 105 provided at the center of theLED-element 102, an n-contact electrode 125 formed longitudinally forbeing electrically connected to the n-side fusion bonding portion 105,and a p-side fusion bonding portion 105 provided at 4 corners of thep-contact electrode 124.

The effects of the fourteenth embodiment are as follows.

Even in the case of the rectangular LED-element 102, a small-size andhigh-brightness LED-element 102 can be obtained by having high currentdiffusivity without significantly decreasing the occupation ratio of thelight emission area to the LED-element 102.

Embodiment 15

FIG. 17A is a plain view illustrating a fusion-bonded portion of an LEDelement according to a fifteenth embodiment of the invention, and FIG.17B is a cross-sectional view cut along line A-A of FIG. 17A.

This LED element 102 is different from that of the eleventh embodimentin structure forming p-side and n-side fusion bonding portion 105 on alarge-size LED element 102 (1 mm×1 mm), and as shown in FIG. 17A, 18p-side fusion bonding portions 105 in the formation region of thep-contact electrode 124, and 2 n-side fusion bonding portions 105outside the formation region of the p-contact electrode 124.

In FIG. 17A, an SiO₂ insulating layer 126 is formed in a portion exceptfor the formation region of the p-side and n-side fusion bonding portion105 and the formation region of the p-contact electrode 124. In theunderlying n-GaN layer 121 of the insulating layer 126, an n-contactelectrode 125 is provided for being electrically connected to the n-sidefusion bonding portion 105 as shown in FIG. 17B. Also, this LED element102 has the n-GaN layer 121 exposed by laser-lifting-off the sapphiresubstrate provided as a base during formation.

The effects of the fifteenth embodiment are as follows.

(1) In the multipoint joining with stud bumps of the large-size LEDelement 102, the multipoint-joining-type element can easily be formedwithout requiring time-consuming provision of a plurality of stud bumpswith good shape accuracy, which allows ensuring realization of costreduction and enhancement in mounting property by reducing processsteps.(2) Since for heat produced by light emission of the large-size LEDelement 102, the arrangement and shape of fusion-bonding portion withexcellent thermal dissipation can be selected without losing currentdiffusivity, both uniform light emission and high thermal dissipationcan be obtained. Although the LED element 102 is 1 mm×1 mm in size,thermal dissipation has to be taken into account even in 0.6 mm×0.6 mmsize, and this structure is effective.(3) In laser-lift-off of the sapphire substrate, in stud bump mounting,to prevent cracking of the GaN-based semiconductor layer, action, suchas underfilling between the circuit pattern and the electrode formationsurface of the LED element 102, has to be taken which increases thenumber of the underfilling step, but in the fifteenth embodiment, sincesubstantially the entire area of the GaN-based semiconductor layer issupported by the fusion bonding portions 105, it is possible tolaser-lift-off the sapphire substrate without underfilling.

Embodiment 16

FIG. 18 is a plain view illustrating a fusion-bonded portion of an LEDelement according to a sixteenth embodiment of the invention.

This LED element 102 has an n-side fusion bonding portion 105 at thecenter of the large-size LED-element 102 explained in the fifteenthembodiment, and an n-contact electrode 125 formed diagonally in a crossshape for being electrically connected to the fusion bonding portion105. This n-contact electrode 125 has a branch portion 125A formed forenhancing current diffusivity.

Also, on the p-contact electrode 124, there are arranged 16 squarep-side fusion bonding portions 105 from which are removed portionscrossing the n-contact electrode 125.

The effects of the sixteenth embodiment are as follows.

(1) In addition to the favorable effects of the fifteenth embodiment,the p-side fusion bonding portions 105 can be formed without beinglimited by the shape and arrangement of the n-side fusion bondingportion 105 and the n-contact electrode 125, which results in alarge-size LED 102 which is excellent in current diffusivity and thermaldissipation.

Also, in the fifteenth embodiment, thermal distribution is asymmetricalon the upper and lower side of the drawing, so that during sealing withlarge thermal expansion coefficient silicon resin, stress in the peelingdirection to the LED element 102 is not entirely but partially uniform,which tends to cause electrical breaking, but in the sixteenthembodiment, thermal distribution is symmetrical on the upper and lowerside and on the right and left side of the drawing, so that stress iscaused entirely uniformly, which has a less incidence of electricalbreaking.

The above LED element 102 may, for example, be flip-chip mounted on asubmount made of Si, for example, followed by being mounted on a leadand subsequently sealed with resin sealing material, such as siliconresin and epoxy resin, which results in an LED 1. In this case, afluorescent material may be mixed into the resin sealing material toform a wavelength conversion type LED 101.

Although the invention has been described with respect to the specificembodiments for complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

1. A light-emitting element, comprising: p and n contact electrodesformed on a flip-chip mounting surface of the light-emitting elementcorresponding to one light-emitting layer of the light-emitting element;and a fusion-bonding portion formed on the p and n contact electrodescorresponding to the p and n contact electrodes, for being directlyfusion-bonded to an external mounting pattern, wherein thefusion-bonding portion comprises a plurality of fusion-bonding portionselectrically connected to the same polarity electrode, and wherein thefusion-bonding portion comprises a thick support layer, and afusion-bonding layer formed on the thick support layer and having athickness less than a thickness of the thick support layer, saidfusion-bonding layer abutting side surfaces of the p and n contactelectrodes, and said thick support layer abutting bottom surfaces of thep and n contact electrodes.
 2. The light-emitting element according toclaim 1, wherein a portion of said light-emitting element comprisingsaid p contact electrode is greater than a portion of saidlight-emitting element comprising said n contact electrode.
 3. Thelight-emitting element according to claim 1, wherein the p-contactelectrode serves as a reflection mirror.
 4. The light-emitting elementaccording to claim 1, wherein the n contact electrode is formed at acentral portion of the light-emitting element.
 5. The light-emittingelement according to claim 1, wherein the fusion-bonding layer formed onthe p and n contact electrodes has substantially a same plane such thatan upper surface of the light-emitting element is parallel to a surfaceof a mounting substrate upon a mounting of the light-emitting element.6. The light-emitting element according to claim 1, wherein thefusion-bonding portion abuts the flip-chip mounting surface of thelight-emitting element.
 7. The light-emitting element according to claim1, wherein an upper surface of the fusion-bonding portion is co-planarwith an upper surface of the p and n contact electrodes.